The present invention relates to a congestion control and avoidance method in a data processing system and more particularly, to a congestion control and avoidance for data traffic between a client and a server in a communication network.
As the Internet has spread quickly, services such as ticket reservation, bank and security transaction, which have been conventionally carried out at the windows of the banks or securities companies, are recently offered via the Internet. Further, since communication technologies are advanced, such an environment has been prepared that people can enjoy various services not only from homes or offices but also from portable phones or the like.
In a conventional method wherein clients demand their service requests directly to a server, clients' requests are likely to become congested at the server. As a result, there will occur such a problem that the capacity of a communication line or the capability of the server cannot cope with requests from many users or clients. Thus, even when a user issues a request many times to the server, sometimes it is hard for the user to receive its response from the server, depending on a period of time or an access destination.
In general, such a problem can be improved by installing a web proxy device. In this case, a request from a client is processed by the web proxy device. Since the web proxy device is provided with a memory (caching module) for storing (caching) a part of past communication contents, the web proxy device can process a request relating to the communication contents stored therein without connecting the request to the server. The web proxy device is use in many communication systems because of its effectiveness.
At present, a large scale web proxy apparatus is usually installed in a communication system capable of handling about 10,000,000 users. In such a communication system, requests to the large scale web proxy apparatus are excessively congested. When such request congestion takes place, a communication line becomes heavy or congested and the load of the apparatus is increased, which results in that users can less enjoy services offered by the communication system. In addition, when such excessive congestion is continued, a trouble (congestion) may take place in the large scale web proxy apparatus, thus leading to stoppage of the operation of the apparatus. Since the stoppage of the operation of the large scale web proxy apparatus means that the apparatus cannot function as a communication system, all the users utilizing the communication system cannot receive the services.